[Letux-kernel] Fwd: Nokia N900 not hitting OFF mode since 5.9 is caused by proactive memory compaction

[H. Nikolaus Schaller]

Hi Andreas,
I have checked:

	http://download.goldelico.com/letux-kernel/letux-5.10.83/src/FULLCONFIG

has CONFIG_COMPACTION=y

But

	http://download.goldelico.com/letux-kernel/letux-5.10.83/src/DEFCONFIG

has not. So it needs to be disabled explicitly. Interestingly letux-5.4.163 has it enabled as well.
So we should also look if the patch identified by Merlijn was already backported...

Since I can't test it (have no proper power-management-test-setup any more),
I will proactively disable it for letux-5.10.y, letux-5.15.y and letux-5.16-rc...

Beste Grüße,
Nikolaus


> Anfang der weitergeleiteten Nachricht:
> 
> Von: Merlijn Wajer <merlijn at wizzup.org>
> Betreff: Nokia N900 not hitting OFF mode since 5.9 is caused by proactive memory compaction
> Datum: 10. Dezember 2021 um 01:39:16 MEZ
> An: linux-omap <linux-omap at vger.kernel.org>, phone-devel at vger.kernel.org, maemo-leste at lists.dyne.org, Tony Lindgren <tony at atomide.com>, Pavel Machek <pavel at ucw.cz>
> Kopie: Sebastian Reichel <sre at kernel.org>, Ivaylo Dimitrov <ivo.g.dimitrov.75 at gmail.com>, Dev Null <devnull at uvos.xyz>, Andreas Kemnade <andreas at kemnade.info>, "H. Nikolaus Schaller" <hns at goldelico.com>
> 
> Hi,
> 
> I've spent the day bisecting what exact commit prevented the Nokia N900
> from entering the OFF sleep state (between v5.8 and v5.9), and it this
> commit:
> 
>> # first bad commit: [facdaa917c4d5a376d09d25865f5a863f906234a] mm: proactive compaction
> 
> The git tree prior to that commit can idle at about ~27mW in OFF mode,
> and it will often remain in that mode for prolonged amounts of time
> (easily 30 seconds, depending on running userspace). Which the above
> commit applied, the Nokia N900 almost never hits OFF mode any more. This
> would suggest at least to disable CONFIG_COMPACTION, perhaps in
> omap2plus_defconfig? I suspect this might cause idle problems beyond the
> Nokia N900, too.
> 
> Maybe nothing needs to be done here other than disable the config option
> -- but I wanted to share this in case others are trying to figure out
> what happened to their battery life. :-)
> 
> There seem be more power regressions since then (at least on 5.15 there
> is more blocking proper idle), so I'll try to find those as well, but if
> this commit is reverted (or CONFIG_COMPACTION=n is in .config - probably
> easier) on top of v5.9 the system seems to idle fine.
> 
>> # grep ^core_pwrdm /sys/kernel/debug/pm_debug/count | cut -d',' -f2,
>> OFF:16,RET:2
> 
> Hope this helps someone...
> 
> Regards,
> Merlijn
> 
> PS: v5.10 seems to use another 19mW if panel_sony_acx565akm is loaded
> even when display is not active (maybe it doesn't suspend or something?
> - could be fixed later, just noticed it for v5.10). I load it initially
> to idle the display, but until I rmmod the modules, the module uses
> quite a bit more power. This problem is not present in v5.9, so that is
> another thing to chase down I guess... And then v5.15 uses another 12mW
> more, for not yet uncovered reasons)